1. Field of the Invention
The present invention relates to a communication control method in a mobile communication system and a base station and a program record medium used therefor, and in particular, to the communication control method of a channel from the base station to a mobile station on soft handover in a CDMA (Code Portion Multiple Access) cellular mobile radio communication system.
2. Description of the Prior Art
One of the cellular mobile communication systems is an HSDPA (High Speed Downlink Packet Access) mode, which is a technology for transmitting packeted data by using a high-speed downlink shared channel (downlink-specific) called HS-PDSCH (High Speed-Physical Downlink Shared Channel) in the case of transmitting to a mobile station large amounts of data (such as the data of a static image and a dynamic image) from a communication network via a base station. It is a mode wherein, in the case where the large amounts of data must be simultaneously transmitted to a plurality of mobile stations, this high-speed downlink shared channel called HS-PDSCH is shared time-wise (time sharing) to use this one high-speed channel by sharing.
When the mobile station approaches a boundary of a cell in such a cellular mobile communication system in the HSDPA mode, the mobile station is in a state capable of communication by setting up channels with a plurality of base stations having the cells near this boundary as their service areas, which is called a soft handover state. At the time of this soft handover, for example, channels are connected between a certain mobile station (MS) 10 and two base stations (BS) 1 and 2 as shown in FIG. 1.
As for these channels, there are two types as shown in FIG. 1, where one type is a downlink-specific common pilot channel called CPICH (Common Pilot Channel), indicated as a CPICH 1 and a CPICH 2 corresponding to the base stations 1 and 2 respectively. In addition, the other type is a dedicated (physical) channel for uplink/downlink called DPCH (Dedicated Physical Channel) and includes various communication data such as control information and voice. It is also indicated as a DPCH 1 and a DPCH 2 corresponding to the base stations 1 and 2 in FIG. 1. Moreover, in FIG. 1, a PDSCH is the above-mentioned large-capacity data channel, which is a downlink-specific shared data channel.
Moreover, definitions of such various channels are disclosed in the 3GPP (3rd Generation Partnership Project) Specifications TS25.211V3.0.0 (1999-10).
It adopts a method wherein, on the soft handover, a plurality of base stations 1 and 2 simultaneously transmit the DPCH to a mobile station 10, and the PDSCH that is the data channel is transmitted by just one base station (only the base stations 1 in FIG. 1) so as to control transmitting power of this PDSCH in accordance with the DPCH, which is disclosed in the 3GPP Report TR25.841V4.0.0 (2000-12).
According to this report, transmitting power PPDSCH from the base station of the PDSCH is determined as follows.
PPDSCH=PDPCH1xc2x7Axc2x7Cxe2x80x83xe2x80x83(1)
Here, the transmitting power of the DPCH1 is PDPCH1, and A is a constant and selected as A=1 for instance. And C is defined as follows.
PCPICH1 greater than PCPICH2
In this case, C=Cprimary (=2 to 3 dB), and if
PCPICH1 less than PCPICH2,
it is C=Cnon-primary (=4 to 6 dB). In addition, PCPICH 1 and PCPICH 2 are the received power of the CPICH 1 and CPICH 2 in the mobile station.
In another mobile communication system for performing data communication from the base station to the mobile station by using the PDSCH, the transmitting power of this PDSCH is not controlled but is fixed, and instead, it is possible to select a plurality of transmission modes of different modulating methods or encoding methods. As for the modulating methods, there are QPSK (Quadrature Phase Shift Keying) capable of transmitting 2 bits (4 values) by 1 symbol, 16 QAM (16 Quadrature Amplitude Modulation) capable of transmitting 4 bits (16 values) by 1 symbol, 64 QAM (64 Quadrature Amplitude Modulation) capable of transmitting 6 bits (64 values) by 1 symbol and soon. In addition, as for the encoding methods, there are convolutional encoding of an encoding ratio xc2xd for performing encoding by 2 bits per information bit, the convolutional encoding of an encoding ratio xc2xd for performing encoding by 3 bits per information bit and so on.
FIG. 11 shows an example of selection of the transmission modes of different modulating methods. In FIG. 11, for instance, the transmission mode is selected so that, a distant from a base station 51 to a mobile station 52 is shorter, a transmitting speed becomes to be faster. To be more specific, the base station 51 selects the transmission modes of 64 QAM, 16 QAM and QPSK in increasing order of distance to the mobile station 52.
While the DPCH is used together with the PDSCH in order to transmit and receive control information on the data transmission by the PDSCH, there is a method in the past, as that of selecting the above-mentioned transmission modes of 64 QAM, 16 QAM and QPSK, wherein a range of the transmitting power in the base station of the DPCH of the downlink is determined in advance so as to select the transmission mode according to that transmitting power.
In this case, the mobile station measures receiving quality of the DPCH from the base station, compares the measured value to a reference value, and notifies the base station of increase or decrease in the transmitting power of the DPCH so that the measured value becomes close to the reference value. The base station increases or decreases the transmitting power of the DPCH according to that notification, and also selects the transmission mode according to the transmitting power set up by the increase or decrease. For instance, as shown in FIG. 12, it selects the transmission modes of the 64 QAM, 16 QAM and QPSK in increasing order of the transmitting power to be set up.
As for the method of determining the transmitting power of the PDSCH shown in the above-mentioned equation (1), it is a two-step control method wherein the transmitting power of the PDSCH is determined by rendering the C of the equation (1) as Cprimary if, of a plurality of base stations in the soft handover state, the base station setting up the PDSCH is one having higher received power of the CPICH in the mobile station (Primary), and by rendering the C as Cnon-primary otherwise, resulting in a problem that continuous and elaborate control cannot be exerted. To be more specific, there is a fault that it is not possible to maintain the receiving quality of the PDSCH at a fixed level regardless of a position of the mobile station 10 on the soft handover.
An object of the present invention is to provide the communication control method in the mobile communication system and the base station and a record medium used therefor, wherein, in the case where the PDSCH is transmitted by one specific base station and the DPCH is simultaneously transmitted by the plurality of base stations while controlling the transmitting power of the PDSCH according to the DPCH, an optimum value of a power ratio between the PDSCH and the DPCH is optimized according to the position of the mobile station, and thus it is possible to maintain the receiving quality of the PDSCH at a fixed level regardless of the position of the mobile station on the soft handover.
In addition, as for the above-mentioned method of selecting the transmission mode, the PDSCH that is the data channel is transmitted by just one base station, while the transmitting power of the DPCH in the base stations is controlled, on the soft handover when the plurality of base stations simultaneously transmit the DPCH to the mobile station, by the receiving quality generated by synthesizing the received DPCH transmitted from the plurality of base stations in the mobile station, resulting in a value different from the transmitting power in the case where only one base station transmits the DPCH, so that there is a fault that it is not possible to adequately select the transmission mode of the PDSCH and maintain the receiving quality of the PDSCH at a fixed level.
Another object of the present invention is to provide the communication control method in the mobile communication system and the base station and the program record medium used therefor, wherein, in the case where the PDSCH is transmitted by one specific base station and the DPCH is simultaneously transmitted by the plurality of base stations while controlling the transmission mode of the PDSCH according to the transmitting power of the DPCH, the transmission mode of the PDSCH is controlled according to the position of the mobile station, and thus it is possible to maintain the receiving quality of the PDSCH at a fixed level regardless of the position of the mobile station on the soft handover.
According to the present invention, it is possible to acquire a communication control method in a mobile communication system wherein a mobile station and a plurality of base stations in a soft handover state with this mobile station setting up a dedicated channel to the above described mobile station and informing a common pilot channel are included, and only a specific base station of the plurality of base stations in the soft handover state has a shared channel with the above described mobile station set up, the above described method characterized by, in the above described mobile station, measuring received power of the above described dedicated channel or common pilot channel transmitted from each of the above described plurality of base stations and notifying the above described specific base station of this measuring results information, and in the above described specific base station, controlling data transmission of the above described shared channel based on transmitting power of the above described dedicated channel and the above described measuring results information, the above described controlling performed according to a ratio between a sum of the above described received power and the received power from the above described specific base station.
According to the present invention, it is possible to acquire the communication control method in the mobile communication system wherein the mobile station and the plurality of base stations in the soft handover state with this mobile station setting up the dedicated channel to the above described mobile station and informing the common pilot channel are included, and only the specific base station of the plurality of base stations in the soft handover state has the shared channel with the above described mobile station set up, the above described method characterized by, in the above described mobile station, measuring the received power of the above described dedicated channel or common pilot channel transmitted from each of the above described plurality of base stations and notifying the above described specific base station of this measuring results information, and in the above described specific base station, performing the data transmission of the above described shared channel by the power determined based on the above described measuring results information and the transmitting power of the above described dedicated channel, and the above described determined power being a value according to the ratio between the sum of the above described received power and the received power from the above described specific base station.
According to the present invention, it is possible to acquire the communication control method in the mobile communication system wherein the mobile station and the plurality of base stations in the soft handover state with this mobile station setting up the dedicated channel to the above described mobile station and informing the common pilot channel are included, and only the specific base station of the plurality of base stations in the soft handover state has the shared channel with the above described mobile station set up, the above described method characterized by, in the above described mobile station, measuring receiving SIR (Signal to Interference Ratio) of the above described dedicated channel or the above described common pilot channel transmitted from each of the above described plurality of base stations and notifying the above described specific base station of this measuring results information, and in the above described specific base station, controlling the data transmission of the above described shared channel based on the transmitting power of the above described dedicated channel and the above described measuring results information, and this controlling performed according to the ratio between the sum of the above described receiving SIR and the receiving SIR from the above described specific base station.
According to the present invention, it is possible to acquire the communication control method in the mobile communication system wherein the mobile station and the plurality of base stations in the soft handover state with this mobile station setting up the dedicated channel to the above described mobile station and informing the common pilot channel are included, and only the specific base station of the plurality of base stations in the soft handover state has the shared channel with the above described mobile station set up, the above described method characterized by, in the above described mobile station, measuring the receiving SIR (Signal to Interference Ratio) of the above described dedicated channel or the above described common pilot channel transmitted from each of the above described plurality of base stations and notifying the above described specific base station of this measuring results information, and in the above described specific base station, performing the data transmission of the above described shared channel by the power determined based on the above described measuring results information and the transmitting power of the above described dedicated channel, and the above described determined power being the value according to the ratio between the sum of the above described receiving SIR and the receiving SIR from the above described specific base station.
According to the present invention, it is possible to acquire the specific base station in the mobile communication system wherein the mobile station and the plurality of base stations in the soft handover state with this mobile station setting up the dedicated channel to the above described mobile station and informing the common pilot channel are included, and only the specific base station of the plurality of base stations in the soft handover state has the shared channel with the above described mobile station set up, the above described specific base station characterized by, in response to the notification of the measuring results information in the above described mobile station on the received power of the above described dedicated channel or the above described common pilot channel transmitted from each of the above described plurality of base stations, controlling the data transmission of the above described shared channel based on the transmitting power of the above described dedicated channel and the above described measuring results information, this controlling performed according to the ratio between the sum of the above described received power and the received power from the above described specific base station.
According to the present invention, it is possible to acquire the specific base station in the mobile communication system wherein the mobile station and the plurality of base stations in the soft handover state with this mobile station setting up the dedicated channel to the above described mobile station and informing the common pilot channel are included, and only the specific base station of the plurality of base stations in the soft handover state has the shared channel with the above described mobile station set up, the above described specific base station characterized by, in response to the notification of the measuring results information in the above described mobile station on the received power of the above described dedicated channel or the above described common pilot channel transmitted from each of the above described plurality of base stations, performing the data transmission of the above described shared channel by the power determined based on this measuring results information and the transmitting power of the above described dedicated channel, and the above described determined power being the value according to the ratio between the sum of the above described received power and the received power from the above described specific base station.
According to the present invention, it is possible to acquire the specific base station in the mobile communication system wherein the mobile station and the plurality of base stations in the soft handover state with this mobile station setting up the dedicated channel to the above described mobile station and informing the common pilot channel are included, and only the specific base station of the plurality of base stations in the soft handover state has the shared channel with the above described mobile station set up, the above described specific base station characterized by, in response to the notification of the measuring results information in the above described mobile station on the receiving SIR (Signal to Interference Ratio) of the above described dedicated channel or the above described common pilot channel transmitted from each of the above described plurality of base stations, controlling the data transmission of the above described shared channel based on the transmitting power of the above described dedicated channel and the above described measuring results information, and this controlling performed according to the ratio between the sum of the above described receiving SIR and the receiving SIR from the above described specific base station.
According to the present invention, it is possible to acquire the specific base station in the mobile communication system wherein the mobile station and the plurality of base stations in the soft handover state with this mobile station setting up the dedicated channel to the above described mobile station and informing the common pilot channel are included, and only the specific base station of the plurality of base stations in the soft hand over state has the shared channel with the above described mobile station set up, the above described specific base station characterized by, in response to the notification of the measuring results information in the above described mobile station on the receiving SIR (Signal to Interference Ratio) of the above described dedicated channel or the above described common pilot channel transmitted from each of the above described plurality of base stations, performing the data transmission of the above described shared channel by the power determined based on this measuring results information and the transmitting power of the above described dedicated channel, and the above described determined power being the value according to the ratio between the sum of the above described receiving SIR and the receiving SIR from the above described specific base station.
According to the present invention, it is possible to acquire a record medium having recorded a control program of the specific base station in the mobile communication system wherein the mobile station and the plurality of base stations in the soft handover state with this mobile station setting up the dedicated channel to the above described mobile station and informing the common pilot channel are included, and only the specific base station of the plurality of base stations in the soft handover state has the shared channel with the above described mobile station set up, the above described program characterized by, including a process of, in response to the notification of the measuring results information in the above described mobile station on the received power of the above described dedicated channel or the above described common pilot channel transmitted from each of the above described plurality of base stations, controlling the data transmission of the above described shared channel based on the transmitting power of the above described dedicated channel and the above described measuring results information, the above described controlling performed according to the ratio between the sum of the above described received power and the received power from the above described specific base station.
According to the present invention, it is possible to acquire the record medium having recorded the control program of the specific base station in the mobile communication system wherein the mobile station and the plurality of base stations in the soft handover state with this mobile station setting up the dedicated channel to the above described mobile station and informing the common pilot channel are included, and only the specific base station of the plurality of base stations in the soft handover state has the shared channel with the above described mobile station set up, the above described program characterized by, including the process of, in response to the notification of the measuring results information in the above described mobile station on the received power of the above described dedicated channel or the above described common pilot channel transmitted from each of the above described plurality of base stations, performing the data transmission of the above described shared channel by the power determined based on this measuring results information and the transmitting power of the above described dedicated channel, and the above described determined power being the value according to the ratio between the sum of the above described received power and the received power from the above described specific base station.
According to the present invention, it is possible to acquire the record medium having recorded the control program of the specific base station in the mobile communication system wherein the mobile station and the plurality of base stations in the soft handover state with this mobile station setting up the dedicated channel to the mobile station and informing the common pilot channel are included, and only the specific base station of the plurality of base stations in the soft handover state has the shared channel with the above described mobile station set up, the above described program characterized by, including the process of, in response to the notification of the measuring results information in the above described mobile station on the receiving SIR (Signal to Interference Ratio) of the above described dedicated channel or the above described common pilot channel transmitted from each of the above described plurality of base stations, performing the data transmission of the above described shared channel by the power determined based on this measuring results information and the transmitting power of the above described dedicated channel, and the above described determined power being the value according to the ratio between the sum of the above described receiving SIR and the receiving SIR from the above described specific base station.
According to the present invention, it is possible to acquire a communication control method in the mobile communication system wherein the mobile station and the plurality of base stations in the soft handover state with this mobile station setting up the dedicated channel to the above described mobile station and informing the common pilot channel are included, and only the specific base station of the plurality of base stations in the soft handover state has the shared channel with the above described mobile station set up, the above described method characterized by: in the above described mobile station, measuring the received power of the above described dedicated channel or common pilot channel transmitted from each of the above described plurality of base stations and notifying the above described specific base station of these measuring results information, and in the above described specific base station, determining one of the plurality of transmission modes of different modulation or encoding methods based on the above described measuring results information and the transmitting power of the above described dedicated channel, and performing data transmission of the above described shared channel in the determined transmission mode, and the above described transmission mode determined based on the value according to the ratio between the sum of the above described received power and the received power from the above described specific base station.
According to the present invention, it is possible to acquire the communication control method in the mobile communication system wherein the mobile station and the plurality of base stations in the soft handover state with this mobile station setting up the dedicated channel to the above described mobile station and informing the common pilot channel are included, and only the specific base station of the plurality of base stations in the soft handover state has the shared channel with the above described mobile station set up, the above described method characterized by, in the above described mobile station, measuring the receiving SIR (Signal to Interference Ratio) of the above described dedicated channel or the above described common pilot channel transmitted from each of the above described plurality of base stations and notifying the above described specific base station of these measuring results information, and in the above described specific base station, determining one of the plurality of transmission modes of different modulation or encoding methods based on the above described measuring results information and the transmitting data of the above described shared channel in the determined transmission mode, and performing the data transmission of the above described shared channel in the determined transmission mode, and the above described transmission mode determined based on the value according to the ratio between the sum of the above described receiving SIR and the receiving SIR from the above described specific base station.
According to the present invention, it is possible to acquire the specific base station in the mobile communication system wherein the mobile station and the plurality of base stations in the soft handover state with this mobile station setting up the dedicated channel to the above described mobile station and informing the common pilot channel are included, and only the specific base station of the plurality of base stations in the soft handover state has the shared channel with the above described mobile station set up, the above described station characterized by: in response to the notification of the measuring results information in the above described mobile station on the received power of the above described dedicated channel or the above described common pilot channel transmitted from each of the above described plurality of base stations, determining one of the plurality of transmission modes of different modulation or encoding methods based on this measuring results information and the transmitting power of the above described dedicated channel, and performing the data transmission of the above described shared channel in the determined transmission mode, and the above described transmission mode determined based on the value according to the ratio between the sum of the above described received power and the received power from the above described specific base station.
According to the present invention, it is possible to acquire the specific base station in the mobile communication system wherein the mobile station and the plurality of base stations in the soft handover state with this mobile station setting up the dedicated channel to the above described mobile station and informing the common pilot channel are included, and only the specific base station of the plurality of base stations in the soft handover state has the shared channel with the above described mobile station set up, the above described station characterized by, in response to the notification of the measuring results information in the above described mobile station on the receiving SIR (Signal to Interference Ratio) of the above described dedicated channel or common pilot channel transmitted from each of the above described plurality of base stations, determining one of the plurality of transmission modes of different modulation or encoding methods based on this measuring results information and the transmitting power of the above described dedicated channel, and performing the data transmission of the above described shared channel in the determined transmission mode, and the above described transmission mode determined based on the value according to the ratio between the sum of the above described receiving SIR and the receiving SIR from the above described specific base station.
According to the present invention, it is possible to acquire the record medium having recorded the control program of the specific base station in the mobile communication system wherein the mobile station and the plurality of base stations in the soft handover state with this mobile station setting up the dedicated channel to the mobile station and informing the common pilot channel are included, and only the specific base station of the plurality of base stations in the soft handover state has the shared channel with the above described mobile station set up, the above described program characterized by, including the process of, in response to the notification of the measuring results information in the above described mobile station on the received power of the above described dedicated channel or the above described common pilot channel transmitted from each of the above described plurality of base stations, determining one of the plurality of transmission modes of different modulation or encoding methods based on this measuring results information and the transmitting power of the above described dedicated channel, and performing the data transmission of the above described shared channel in the determined transmission mode, and the above described transmission mode determined based on the value according to the ratio between the sum of the above described received power and the received power from the above described specific base station.
According to the present invention, it is possible to acquire the record medium having recorded the control program of the specific base station in the mobile communication system wherein the mobile station and the plurality of base stations in the soft handover state with this mobile station setting up the dedicated channel to the above described mobile station and informing the common pilot channel are included, and only the specific base station of the plurality of base stations in the soft handover state has the shared channel with the above described mobile station set up, the above described program characterized by: including the process of, in response to the notification of the measuring results information in the above described mobile station on the receiving SIR of the above described dedicated channel or common pilot channel transmitted from each of the above described plurality of base stations, determining one of the plurality of transmission modes of different modulation or encoding methods based on this measuring results information and the transmitting power of the above described dedicated channel, and performing the data transmission of the above described shared channel in the determined transmission mode, and the above described transmission mode determined based on the value according to the ratio between the sum of the above described receiving SIR and the receiving SIR from the above described specific base station.
In addition, the above described transmission mode may also be determined based on the value acquired by multiplying the transmitting power of the above described dedicated channel by the ratio between the sum of the above described received power and the received power from the above described specific base station. Moreover, the above described transmission mode may also be determined based on the value acquired by multiplying the transmitting power of the above described dedicated channel by the ratio between the sum of the above described receiving SIR and the receiving SIR from the above described specific base station
Workings of the present invention will be described. The mobile station notifies the specific base station (the base station for transmitting a PDSCH) of each of the above measuring results, and the specific base station notified thereof multiplies the transmitting power of a DPCH that is the dedicated channel transmitted by the base station by a coefficient determined based on these measuring results so as to control transmission by using that multiplication value.
To mention it further, when the transmitting power of the dedicated channel is controlled so that receiving quality of the signal of the dedicated channel transmitted from one base station becomes fixed, that transmitting power reflects a propagation loss from the base station to the mobile station and a link state of noise power and interference wave power in the mobile station.
Accordingly, in the case of performing the data transmission by using the shared channel from that base station, it is possible to exert control reflecting the link state by controlling the data transmission according to the transmitting power thereof.
However, when the transmitting power of the dedicated channel is controlled by synthesizing the signals of the dedicated channels transmitted from the plurality of base stations in the mobile station performing the soft handover so that the receiving quality of the synthesized signals becomes fixed, that transmitting power does not correctly reflect the link state from the specific base station to the mobile station for performing the data transmission using the shared channel. It is because the receiving quality of the synthesized signal also depends on the signals from the base stations other than the specific base station.
According to the method of the present invention, it is possible to exert control not only using the transmitting power of the dedicated channel, but also estimating a difference between the receiving quality of the signal from the specific base station and that of the signal wherein the signals from the plurality of base stations including the specific base station are synthesized and reflecting the link state from the specific base station to the mobile station by using the difference.
For that reason, even if the link state changes due to the position of the mobile station, it is possible to maintain the link quality of the data transmission at a fixed level and improve efficiency of the data transmission.
To be more specific, the mobile communication system for controlling the transmitting power of the PDSCH controls the value of the ratio between the transmitting power of the PDSCH and the transmitting power of the DPCH that is the dedicated channel so that it becomes the ratio determined based on the measured values (receiving quality) of the received power and the receiving SIR (Signal to Interference Ratio) of the common channel or the dedicated channel in the mobile station so as to be optimized according to the position of the mobile station on the soft handover in the base station for transmitting the PDSCH that is a large-capacity shared data transmission line.
In addition, the mobile communication system capable of selecting the transmission mode of the PDSCH controls the transmission mode so that the transmitting power per information bit transmitted by the PDSCH is determined based on the measured values (receiving quality) of the received power and the receiving SIR (Signal to Interference Ratio) of the common channel or the dedicated channel in the mobile station so as to be optimized according to the position of the mobile station on the soft handover in the base station for transmitting the PDSCH that is a large-capacity shared data transmission line.